This is the best explanation I could find from Canon of what exactly the cleaning does: "Self Cleaning Sensor Unit is activated to automatically shake off the dust on the front of the sensor (CMOS)." Source. Not overly helpful, is it?
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nchpmnApr 9 '11 at 8:11

1

My first DSLR had no anti-dust system and dust spots were an ongoing problem requiring regular cleaning. 16 months ago I bought an upgrade with anti dust coating on the sensor and the high frequency sensor shake on start up. Since then I have had no problems, my DSLR sensor has not required cleaning. From my experience it really does work. But this is not strictly relevant to your question since I use neither Nikon nor Canon.
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labnutApr 9 '11 at 12:24

This isn't just Canon/Nikon. When these systems first came out, tests showed that Olympus's was the only one that actually worked. Others have improved since then, though. Like @labnut, my first camera with this feature (a Pentax K100D) had constant dust problems. Since getting the Pentax K-7, though, it's no longer an issue, even though I change lenses much more often than I used to.
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mattdmApr 9 '11 at 12:42

4 Answers
4

Shaking the dust does help, but it won't remove all the dust. Some particles will cling to the filter glass in front of sensor hard enough not to be shaken out. Moisture and fat particles will gladly help with the clinging. The sensor still has to be cleaned now and then, but interval is somewhat longer than without shake. Before important shootings, the sensor should be cleaned and checked manually, the shake system is not reliable enough.

The dust is meant to fall on an adhesive strip below the sensor, so it will work best if the camera is held horizontally in landscape orientation during the shake.

I know that Nikon started using anti-static tin oxide coating at some point, but Canon has used anti-static materials on self-cleaning sensors since 400D, so I'm not sure if they have improved anything since then.

Nikon has a similar system on many newer models starting from D60 and D90. Pentax cameras have had it since K100D Super and K10D.

You asked how effective the sensor dust removal systems are for Nikon and Canon cameras and whether they have improved.

To answer the questions I searched the DPReview forums for mentions of sensor dust.
The search was conducted first for the entire period of all known postings and then for the last 12 months only.

The search of all postings confirmed the subjective impressions that at one time dust on sensors was a major concern for both Canon and Nikon owners, with Canon owners seemingly more affected than Nikon owners (0.94% vs 0.64%).

The search during the last 12 month period shows a dramatic four fold improvement for both Canon and Nikon owners, but with the Nikon results still slightly better (0.16% vs 0.20%).

This is striking confirmation of the subjective impressions that modern dust removal systems are greatly improved.

Methodology
DPReview was chosen because it has a large volume of postings covering a period of many years.
The following commands were used to search Google and the number of replies are the figures quoted in this study. This was done for the last 12 months and for the entire time period.
sensor dust "forum=1034" site:http://forums.dpreview.com/forums
sensor dust "forum=1039" site:http://forums.dpreview.com/forums
sensor dust "forum=1021" site:http://forums.dpreview.com/forums
"forum=1034" site:http://forums.dpreview.com/forums
"forum=1039" site:http://forums.dpreview.com/forums
"forum=1021" site:http://forums.dpreview.com/forums

Caveats
The absolute number of complaints has no useful meaning since it is a self selected sample that may contain multiple mentions of the same problem. But it forms a good basis for making comparisons. The large number of postings, ca. four million for both Canon and Nikon are enough to give reasonable confidence in the comparisons.

Now this is an impressive job you've done. I'm not accepting it as the correct answer because you've conducted an empirical survey on dust removal improvement in technology but not directly answered my questions. Anyway. I would vote you up several times if I could of course. But I can easily see others that will vote you up as well surpassing accepted answer. Great job labnut. Thank you for this in-depth research.
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Robert KoritnikApr 10 '11 at 8:28

This might show that dust removal has improved. I think, more likely, it shows that people are complaining less about sensor dust, now that it's been widely understood, talked to death on forums like dpreview, and accepted as a fact of life. I think it also shows that Canon users are more likely to discuss their cameras online, not that Canon has bigger dust issues.
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ruiefNov 17 '14 at 22:07

I can't find the link right now, but someone ran an experiment where he put dust on the sensors of several cameras (of different brands) and tested how much remained after running the camera's self-cleaning function many times. The results, as I recall, indicated that no brand was very effective at self-cleaning.

I'm not exactly sure, but I believe the idea is largely to prevent dust from sticking to the sensor rather than to remove it from the camera itself.

4) Yes, every time I turn my D5000 off or on it runs a sensor clean, and I can force one in the menus.

As for the effectiveness, I've had the camera for a couple of years and have never had a problem with spots on the sensor. I am fairly careful when I change lenses (i.e. do it fast and turn the camera off) but no more than the next person I would say.